In Tajo, the capacity of running tasks in parallel are determined by available resources and workload of running queries. In order to specify it, please see [Worker Resources] (#ResourceConfiguration) section.

Each worker can execute multiple tasks simultaneously.
In Tajo, users can specify the total size of memory and the number of disks for each worker. Available resources affect how many tasks are executed simultaneously.

In order to specify the resource capacity of each worker, you should add the following configs to tajo-site.xml :

If tajo.worker.resource.dfs-dir-aware is set to true in tajo-site.xml, the worker will aware of and use the number of HDFS datanode’s data dirs in the node.
In other words, tajo.worker.resource.disks is ignored.

Tajo provides a dedicated mode that allows each worker in a Tajo cluster to use whole available system resources including cpu-cores, memory, and disks. For this mode, a user should add the following config to tajo-site.xml :